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We study the reionization scenario in which ionizing UV photons emitted from decaying particle, in addition to usual contributions from stars and quasars, ionize the universe. It is found that the scenario is consistent with both the first…
The first luminous objects forming in the universe produce radiation backgrounds in the FUV and X-ray bands that affect the formation of Population III stars. Using a grid of cosmological hydrodynamics zoom-in simulations, we explore the…
We extend the existing analytical model of reionization by Furlanetto et al. (2004) to include the biasing of reionization sources and additional absorption by Lyman Limit systems. Our model is, by construction, consistent with the observed…
We present a study of the co-evolution of a population of primordial star-forming minihalos at Cosmic Dawn. In this study, we highlight the influence of individual Population III stars on the ability of nearby minihalos to form sufficient…
Many lines of evidence suggest that nonbaryonic dark matter constitutes roughly 30% of the critical closure density, but the composition of this dark matter is unknown. One class of candidates for the dark matter is compact objects formed…
Population III stars, the first generation of stars formed from primordial Big Bang material with a top-heavy IMF, should contribute substantially to the Universe reionization and they are crucial for understanding the early metal…
We use a semi-analytical model to study the impact of reionization, and the associated radiative feedback, on galaxy formation. Two feedback models have been considered: (i) a standard prescription, according to which star formation is…
We present constraints on the reionization optical depth, $\tau$, obtained using several independent methods. First, we perform a non-parametric reconstruction of the reionization history, using Lyman-$\alpha$ constraints on the evolution…
Based on the work by Mitra, Choudhury & Ferrara (2010), we obtain model-independent constraints on reionization from cosmic microwave background (CMB) and QSO absorption line data by decomposing the function N_{ion}(z) (the number of…
A deep understanding of the Epoch of Reionization is still missing in our knowledge of the universe. While future probes will allow us to test the precise evolution of the free electron fraction from redshifts between $z\simeq 6$ and…
The recently revised cosmological constraints from the Five-Year WMAP data ameliorate previous tension between cosmological constraints from the microwave background and from cluster abundances. We demonstrate that the revised estimates of…
Statistical observations of the epoch of reionization (EOR) power spectrum provide a rich data set for understanding the transition from the cosmic "dark ages" to the ionized universe we see today. EOR observations have become an active…
Observing the first generation of Population III (Pop III) stars is one of the most demanding challenges in astronomy. Indeed, Pop III stars are expected to predominantly form within faint minihalos at early times with a top-heavy initial…
We revisit the possibility of constraining the properties of dark matter (DM) by studying the epoch of cosmic reionization. Previous studies have shown that DM annihilation was unlikely to have provided a large fraction of the photons that…
Constraints on the ionization structure of the Intergalactic Medium are derived as directly imposed by observations in conjunction with the results of numerical simulations for structure formation. Under the assumption that the population…
Using the technique of Angulo & White (2010) we scale the Millennium and Millennium-II simulations of structure growth in a LCDM universe from the cosmological parameters with which they were carried out (based on first-year results from…
We constrain the history of reionization using the data from Planck 2015 Cosmic Microwave Background (CMB) temperature and polarization anisotropy observations. We also use prior constraints on the reionization history at redshifts…
We calculate the evolution of Li6 generated from cosmic rays produced by an early population of massive stars. The computation is performed in the framework of hierarchical structure formation and is based on cosmic star formation histories…
Improved measurement of the Cosmic Microwave Background polarization from Planck allows a detailed study of reionization beyond the average optical depth. The lower value of the optical depth disfavours an early onset and an early…
We calculate evolution and nucleosynthesis in massive Pop III stars with M = 13 ~ 270Msun, and compare the results with abundances of very metal-poor halo stars. The observed abundances can be explained by the energetic core-collapse…